I am currently running a NGK R5671a7 and need a hotter plug. I have a 388 with Dart pro 1 heads running 10.8:1 compression with a mini ram set up with SLP headers and need a small plug to avoid the boot touching the headers.

 

i guess that number would be thier "6" Heat range but you probably would use a colder spark plug for a engine like that with cast heads... but with aluminum it is hard to say...

what makes you think you need hotter? a pick of one of the plugs you have now would be great...

 

The plug has carbon build up on them big time and they are a little wet from fuel, worried about fouling a plug. These were inst. new and have dyno time and 300 miles on them. I will post a pick later tonight.

 

well if they where in a brand new engine i could see the carbon fouling do to unseated rings... i would clean them up real good stick them back in and have a small blast through the gears and pull them again and see how they look

 

I'd be looking at the heat line on the ground strap to judge if the plug is the right heat range. All other indications point to fuel mixture or ignition.
With 10.8:1 I wouldn't be wanting a hotter plug!

 

Here is a pick.

 

i think that is due to fuel or oil not heat range

 

Your heat line is good, or just a hair too hot.
That looks like oil sludge to me.